Timeline Adapter

DummyContent.java

package mobi.glowworm.demo.timeline.dummy;

import android.support.annotation.Nullable;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import mobi.glowworm.demo.timeline.TimelineItem;

/**
 * Helper class for providing sample content for user interfaces created by
 * Android template wizards.
 * <p/>
 * TODO: Replace all uses of this class before publishing your app.
 */
public class DummyContent {

    /**
     * An array of sample (dummy) items.
     */
    public static final List<TimelineItem> ITEMS = new ArrayList<>();

    /**
     * A map of sample (dummy) items, by ID.
     */
    public static final Map<String, DummyItem> ITEM_MAP = new HashMap<String, DummyItem>();

    private static final int COUNT = 25;

    static {
        // Add some sample items.
        for (int i = 1; i <= COUNT; i++) {
            addItem(createDummyItem(i));
        }
    }

    private static void addItem(DummyItem item) {
        ITEMS.add(item);
        ITEM_MAP.put(item.id, item);
    }

    private static DummyItem createDummyItem(int position) {
        return new DummyItem(String.valueOf(position), "Item " + position, makeDetails(position));
    }

    private static String makeDetails(int position) {
        return "Details about Item: " + position;
    }

    /**
     * A dummy item representing a piece of content.
     */
    public static class DummyItem implements TimelineItem {
        public final String id;
        public final String content;
        public final String details;

        public DummyItem(String id, String content, String details) {
            this.id = id;
            this.content = content;
            this.details = details;
        }

        @Override
        public String toString() {
            return content;
        }

        @Override
        public int getState() {
            return TimelineItem.STATE_DEFAULT;
        }

        @Nullable
        @Override
        public CharSequence getTime() {
            return String.valueOf(id);
        }

        @Nullable
        @Override
        public CharSequence getPrimaryText() {
            return content;
        }

        @Nullable
        @Override
        public CharSequence getSecondaryText() {
            return details;
        }

        @Override
        public int getMarkerResId() {
            return android.R.drawable.ic_menu_compass;
        }

        @Override
        public int getTimelineResId() {
            return android.R.drawable.ic_menu_compass;
        }
    }
}

item_list_timeline_default.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_vertical"
    android:orientation="horizontal">

    <TextView
        android:id="@+id/tvTLTime"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="@dimen/text_margin"
        android:text="10pm"
        android:textAppearance="@style/TextAppearance.AppCompat.Body1" />

    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="match_parent">

        <ImageView
            android:id="@+id/ivTLTimeline"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:background="@color/colorPrimary" />

        <ImageView
            android:id="@+id/ivTLMarker"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:layout_centerVertical="true" />
    </RelativeLayout>

    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_margin="@dimen/text_margin"
        android:layout_weight="1"
        android:orientation="vertical">

        <TextView
            android:id="@+id/tvTLPrimary"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Heading"
            android:textAppearance="@style/TextAppearance.AppCompat.Body2" />

        <TextView
            android:id="@+id/tvTLSecondary"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Description of something interesting"
            android:textAppearance="@style/TextAppearance.AppCompat.Caption" />
    </LinearLayout>
</LinearLayout>

ItemListActivity.java

package mobi.glowworm.demo.timeline;

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.View;

import mobi.glowworm.demo.timeline.dummy.DummyContent;

public class ItemListActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_item_list);

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        toolbar.setTitle(getTitle());

        View recyclerView = findViewById(R.id.item_list);
        assert recyclerView != null;
        setupRecyclerView((RecyclerView) recyclerView);

    }

    private void setupRecyclerView(@NonNull RecyclerView recyclerView) {
        recyclerView.setAdapter(new TimelineAdapter(DummyContent.ITEMS));
    }
}

TimelineAdapter.java

/*
 * Copyright (C) 2016 Glowworm Software
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
package mobi.glowworm.demo.timeline;

import android.support.annotation.LayoutRes;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.List;

/**
 * A simple {@link RecyclerView.Adapter} implementation for displaying {@link TimelineItem} rows.
 */
public class TimelineAdapter
        extends RecyclerView.Adapter<TimelineAdapter.ViewHolder> {

    /**
     * Implement this to provide a layout resource that can be displayed on the timeline.
     * <p/>
     * This layout should contain fields with the following predefined resource identifiers:
     * <ul>
     * <li>{@link R.id#tvTLTime}</li>
     * <li>{@link R.id#tvTLPrimary}</li>
     * <li>{@link R.id#tvTLSecondary}</li>
     * <li>{@link R.id#ivTLMarker}</li>
     * <li>{@link R.id#ivTLTimeline}</li>
     * </ul>
     *
     * @param viewType The view type of the new View.
     * @return a layout resource that holds a View of the given view type.
     */
    @LayoutRes
    protected int getViewHolderResId(int viewType) {
        return R.layout.item_list_timeline_default;
    }


    @NonNull
    private final List<TimelineItem> items;

    public TimelineAdapter(@NonNull List<TimelineItem> items) {
        this.items = items;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext())
                .inflate(getViewHolderResId(viewType), parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(final ViewHolder holder, int position) {
        holder.item = items.get(position);
        if (holder.tvTime != null) {
            holder.tvTime.setText(items.get(position).getTime());
        }
        if (holder.tvPrimary != null) {
            holder.tvPrimary.setText(items.get(position).getPrimaryText());
        }
        if (holder.tvSecondary != null) {
            holder.tvSecondary.setText(items.get(position).getSecondaryText());
        }
        if (holder.ivMarker != null) {
            holder.ivMarker.setImageResource(items.get(position).getMarkerResId());
        }
        if (holder.ivTimeline != null) {
            holder.ivTimeline.setImageResource(items.get(position).getTimelineResId());
        }
    }

    @Override
    public int getItemCount() {
        return items.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {
        public final View vRoot;

        public final TextView tvTime;
        public final TextView tvPrimary;
        public final TextView tvSecondary;
        public final ImageView ivMarker;
        public final ImageView ivTimeline;

        public TimelineItem item;

        public ViewHolder(View view) {
            super(view);
            vRoot = view;
            tvTime = (TextView) view.findViewById(R.id.tvTLTime);
            tvPrimary = (TextView) view.findViewById(R.id.tvTLPrimary);
            tvSecondary = (TextView) view.findViewById(R.id.tvTLSecondary);
            ivMarker = (ImageView) view.findViewById(R.id.ivTLMarker);
            ivTimeline = (ImageView) view.findViewById(R.id.ivTLTimeline);
        }

        @Override
        public String toString() {
            if ((item == null) || (item.getSecondaryText() == null)) {
                return null;
            }
            return item.getSecondaryText().toString();
        }
    }
}

TimelineItem.java

/*
 * Copyright (C) 2016 Glowworm Software
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
package mobi.glowworm.demo.timeline;

import android.support.annotation.DrawableRes;
import android.support.annotation.Nullable;


/**
 * Abstracted interface to represent basic information that can be displayed by items on a timeline.
 * <p/>
 * Items to be shown in the {@link TimelineAdapter} implement this interface.
 */
public interface TimelineItem {

    /**
     * Default state that can be returned by {@link #getState()}.
     */
    int STATE_DEFAULT = 0;

    /**
     * Timelines often show items in different colours or icons based on some intrinsic state.
     *
     * @return integer value to determine what state this item is in
     */
    int getState();

    /**
     * Timelines often display a date or time value on the left.
     *
     * @return text to display in the date/time/distance field; or null to hide the field
     */
    @Nullable
    CharSequence getTime();

    /**
     * Timelines often display 2 lines of text. This method returns the main "header" or
     * "title" text to display.
     *
     * @return text to display as the header for the row; or null to hide the field
     */
    @Nullable
    CharSequence getPrimaryText();

    /**
     * Timelines often display 2 lines of text. This method returns the secondary "description"
     * to display.
     *
     * @return text to display as the description for the row; or null to hide the field
     */
    @Nullable
    CharSequence getSecondaryText();

    /**
     * Timelines often display an icon for each row.
     *
     * @return resource ID of a drawable to display as the marker for this row; or zero to
     * hide the field
     */
    @DrawableRes
    int getMarkerResId();

    /**
     * Timelines often display a vertical line linking the items. Sometimes this is a single
     * line, all the same colour, and sometimes it can be broken in places, or take on different
     * colours depending on the value of the {@link #getState()} method.
     *
     * @return resource ID of a drawable to display as the section of the timeline contained
     * in this row; or zero to hide the timeline for this row
     */
    @DrawableRes
    int getTimelineResId();
}

Clean-room implementation of a Timeline adapter that uses an abstracted interface that can be reused across multiple "timeline" style lists.

Initial version is taken from the Android Master-Detail new project.

Abstracted out a Timeline interface to represent items in the list. Actual data objects implement this interface.

The adapter uses the interface methods to display information on each row.

Current version requires a given layout file, with predefined field IDs.